Pretreatment process of soybean oil

1. Cleaning of soybean oil

Objectives and requirements:Oil will be mixed with impurities during harvesting, transportation and storage. Although oil is usually cleaned before storage, it will still contain a small amount of impurities after initial cleaning, which can not meet the requirements of oil production. Therefore, after the oil enters the production workshop, it will be further cleaned up, and the content of the impurities will be reduced to the range of the process requirements in order to ensure the production process effect and the quality of the products.

Cleaning methods

  1. Screening:Screening is the use of oil and impurities in the size of the particle size, with the aid of the mixed oil and the sieve surface relative motion, through the sieve hole to be larger or less than the impurities removed from the oil. The screening equipment commonly used in oil refineries includes vibrating screen, plane rotary screen and rotary screen. Most of the screening devices have an important work component, that is, screen surface. The size of sieve holes and the shape of sieve holes should be determined according to the actual size of oilseeds.
  2. Wind separation:According to the difference in the specific gravity and aerodynamic characteristics of oil seeds and impurities, the method of separating impurities from oil by wind is called wind separation.Wind separation can be used to remove light impurities ,dust in oil and heavy metals such as metals and stones. It can also be used for separating kernels and shells after oil shelling. Most of the wind separation equipment selected by general oil plants are combined with screening equipment. For example, air suction screen, vibration cleaning screen and plane rotary sun are equipped with air separation devices. For example, the wind separator is a special equipment for scavenging heavy impurities in cottonseed.
  3. Gravity method to remove stone: The method is based on the proportion of oil seed and stone and the different suspension speed, and the purpose of grading the stone is to use the combined action of the inclined sieve surface with certain motion characteristics and the air flow through the sieve surface.At present, the oil processing plant is often used to absorbing-air gravity stoning machine, which is characterized by the negative pressure in the stoning machine at work, which can effectively prevent the dust from spreading, and the single machine has a large output capacity, but the system of suction and dust removal needs to be configured alone.The blowing-air gravity stoning remover has its own fan with simple structure, but its working conditions are poor and its output is small. It is only used for small oil processing plants.
  4. Magnetic separation:Magnetic separation is a method of removing magnetic metal impurities in oil by magnetic force. The application of magnetic separation is to make use of the magnetic difference of various ores or materials to select other processes under the action of magnetic force and other forces. The equipment commonly used for magnetic separation is permanent magnet drum magnetic separator, cylinder magnetic separator, rotary drum type iron suction machine and charged electromagnetic iron suction machine.
  5. Cleaning of slime:The size of the slime is similar to or equal to that of the oil seeds, and the specific gravity is similar to that of the oil seeds.There are more slime in rapeseed, soybean and sesame seeds. Based on different mechanical performance of the slime, we should grind the oil seeds with slime, and then the small slime should be filtered or selected out by wind. The equipment used for grinding mud mainly consists of rubber roller mill and vertical round sieve.
  6. Dust-removing:The dust contained in the oil not only affects the quality of oil and meal, but also flies in the process of cleaning and transporting the oil. These flying dust pollutes the air and affects the environmental sanitation of the workshop, so it must be cleared.The method of dust removal is firstly the closed dust source, reducing the influence range of the dust, then setting the dust net, concentrating the dust air and removing the dust. There are centrifugal dust remover and bag type dust collector commonly used in oil refinery. Consider the cost and other factors, using centrifugal dust remover.


2. Humidity control of soybean

The water content of oil has an effect on the physical properties of the oil, such as elasticity, plasticity, mechanical strength, thermal conductivity, structure and so on, and the physical properties of the oil directly affect the effect of the oil processing. The water content of oil can also affect the activity of various enzymes in the oil, and the action of the enzyme can change the properties of some components in the oil, and then affect the quality and yield of the products and by-products.If the oil humidity is too high, it must be dried. Convection drying and conduction drying are commonly used.If the moisture of the oil is too small, it should be humidified. Generally, after mixing with saturated steam and water, it can be injected into the oil in conveying. It can achieve better wetting effect and the time of moisture uniformity is also short.


3. Crushing

Before the soybean is rolled, the large granule soybean must be broken.The purpose is to make the soybean grain size meet the rolling conditions by crushing. The surface area of Soybean after breaking increases, which is favorable for softening temperature and moisture transfer and softening effect.

After the soybean is broken, the grain size is uniform, no oil coming out, no agglomeration, little powder, and the particle size meets the requirements. There are several ways to crush oil, such as impact, shear, extrusion and milling. Commonly used crushing equipment is toothed roll crusher, hammer crusher, disc sheller. The broken selection of the toothed roller crusher here.


4. The softening of soybean oil

Softening is to improve the elastoplastic properties of the oil by adjusting the moisture and temperature of the oil, so that it has the best condition for rolling, reducing the powder degree and the sticky roll phenomenon, and ensuring the quality of the slab. The softening is mainly used for oil-bearing materials with low oil content, low water content and high shell content, poor plasticity and hard texture. As the oil content of soybean is low and its plasticity is poor ,soybean need to be softened. Commonly used softening equipment is a layer softening pan and roller softening pot. The roller softening pot with better softening effect is selected here.


5. Flake rolling

Flake rolling is the process of pressing the oil into granular by means of mechanical action.The purpose of rolling is to destroy the cell and tissue of the oil, increase the surface area of the oil, and shorten the distance of the oil outflow,which will be beneficial to the extraction of oil and also improve evaporation effect. Rolling is the key of pretreatment, which is related to the yield and quality of oils . In order to ensure the quality of rolling, the moisture and temperature of the material before rolling should be strictly controlled.

The thinner the average oil is, the more damaged the cell tissue is, the better the oil extraction effect is.Whether the oil is extracted by squeezing or the oil is extracted by solvent, the thickness of the billet has great influence on the oil yield.

Effect of the thickness of bean flake on the oil rate

Oil content of soybean Flake thickness (mm)

Oil yield


0.5 13.58
18.35 0.8


The rolling equipment can be divided into two types: straight line rolling machine and horizontal rolling mill.


6. Extrusion of soybean

Oil extrusion is a process of extruding and expanding equipment to transform crushed, rolled or whole oil into porous expanded pellets.Extrusion is a kind of high temperature and short time treatment process. There are two types of extruders: single screw and twin screw extruder. The pretreatment of oil is currently mainly used for low moisture content.

Single screw extruder treatment, namely: after the oil is cleaned and rolled into the extruder, it is heated, pressed, glued and decompressed. The content can be divided into wet and dry extrusion methods.

At present, there are two main types of extruded oil extruding equipment, one is the expansion machine for low oil containing raw materials, that is, the so-called closed wall extruder, one is used for the puffer with high oil content, that is, the so-called slotting wall extruder.

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